<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>分组选择器</title>
    <style type="text/css">
        h1, h2, h3 {
            color: red;
        }
    </style>
</head>
<body>
    <h1>HTML</h1>
    <h2>CSS</h2>
    <h3>JavaScript</h3>
</body>
</html>